Water absorption is the water uptake by plants. Water is absorbed from soil and eventually reaches the leaves after being distributed to all parts of the plants. There are two types of absorption done by plants, active and passive. Now the main difference between active water absorption and passive water absorption is, in active water absorption the roots of plants absorb water by their own efforts. It takes place even when the rate of transpiration is low. The root cells play an important role in absorbing the water, in this process. On the other hand, in passive absorption of water, root cells do not play any role in absorbing water, they remain passive. Absorption of water occurs when rate of transpiration is high.
Active Water Absorption
In active water absorption of water, plant’s root hair cells absorb the water from the roots even when the rate of transpiration is low. This water id conducted and then distributed to the whole plant, eventually reaching the leaves. ATP is used in active transport to pump molecules against the concentration gradient, from the area of low of solute to high concentration of solute. This process requires cellular energy. In active transport, particles like proteins, large cells, ions and sugar are transported. Types of active transport are endocytosis, exocytosis, cell membrane/sodium-potassium pump. It transports molecule through cell membrane against the concentration gradient so that more nutrient enters the cell.
Passive Water Absorption
In passive water absorption, root hair cells stay passive and they do not take part in absorbing water from the soil. Passive transport occurs when rate of transpiration is really high, due to activity of upper part of plants like shoot and leaves. Active transpiration occurs in the upper part of the plant in passive water absorption. In passive transport, movement of concentration occurs down the gradient. It goes from high concentration to lower concentration, to maintain equilibrium. Types of passive water absorption are diffusion, osmosis and facilitated diffusion. It maintains equilibrium inside the cell. Waste is diffused out and excreted and nutrients are diffused into the cells.
- Active water absorption occurs via root hair cells and passive water absorption occurs when transpiration rate is high.
- Active absorption involves symplast movement of water and passive absorption involves apoplast movement of water.
- Active absorption utilizes metabolic energy and passive absorption utilizes solar energy for transpiration.
- Active absorption is independent of transpiration and passive depends upon transpiration.
- Water is absorbed by osmotic and non osmotic process in active absorption. Water is absorbed as a result of tension created by transpiration pull in passive absorption.